1. Field of the Invention
The invention relates to a ceramic transport shaft, particularly for horizontal continuous melting furnaces for heating glass plates to the bending or tempering temperature.
2. Description of the Related Art
Ceramic transport or conveying shafts such as are, e.g., used in the hot part of roller-type furnaces for heating glass plates to the bending and/or tempering temperature, are in many cases provided with metal end caps used for coupling the transport shafts to a rotary drive mechanism or the rotary mounting of the transport shafts.
The fixing of the end caps to the ceramic transport shafts is problematic, because the shafts are subject to considerable heating during operating and the shaft ends with the end caps reach temperatures of a few hundred degrees C. As the thermal expansion coefficient of the metal forming the end cap is much higher than that of the ceramic material of the transport shafts, the metal cap is enlarged, so that it becomes detached from the shaft end. Therefore, additional measures must be taken to prevent the end cap from becoming detached from the shaft end at elevated temperatures.
U.S. Pat. No. 4,404,011 discloses a transport shaft with a metal end cap, in which the internal diameter of the metal end cap is larger than the external diameter of the shaft end, and in the resulting gap between the shaft end and the end cap are placed a plurality of tensioned leaf springs in such a way that the central area of the leaf springs presses against the circumferential surface of the shaft end, while the end areas of the leaf springs are supported on the inner wall of the end cap. At ambient temperature the pretension of the leaf springs is so high that the necessary compression action can still be exerted by them if there is a radial increase in the size of the gap between the shaft end and the end cap on increasing the temperature. However, there are limits to the use of this solution in that the leaf springs lose their elastic qualities at higher temperatures, so that the end cap fastening can only be used at relatively low temperatures.